first=float(input('输入第一个数'))
second=float(input('请输入第二个数'))
operator=input('请选择运算符:+,-,*,/')
if operator=='+':
    print(first+second)
elif operator=='-':
    print(first+second)
elif operator=='*':
    print(first*second)
elif operator=='/':
    if second==0:
        print('除数不能为零')
    else:
        print(first/second)
